Annular airflow actuation system for variable cycle gas turbine engines

ABSTRACT

An annular airflow control system for a gas turbine engine includes a sync ring rotatable to move a multiple of contra-rotating variable vanes between an open position and a closed position to throttle an airflow through said multiple of contra-rotating variable vanes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This disclosure was made with Government support under FA8650-09-D-2923awarded by The United States Air Force. The Government has certainrights in this disclosure.

BACKGROUND

The present disclosure relates to variable cycle gas turbine engines,and more particularly to an annular airflow control system therefor.

Variable cycle gas turbine engines power aircraft over a range ofoperating conditions yet achieve countervailing objectives such as highspecific thrust and low fuel consumption. The variable cycle gas turbineengine essentially alters a bypass ratio during flight to matchrequirements. This facilitates efficient performance over a broad rangeof altitudes and flight conditions to generate high thrust forhigh-energy maneuvers yet optimize fuel efficiency for cruise andloiter.

Variable cycle gas turbine engines require an effective actuation systemto vary the cycle of a third stream bypass airflow to operate the engineat various cycle points.

SUMMARY

An annular airflow control system for a gas turbine engine according toone disclosed non-limiting embodiment of the present disclosure includesa sync ring rotatable to move a multiple of contra-rotating variablevanes between an open position and a closed position to throttle anairflow through the multiple of contra-rotating variable vanes.

A further embodiment of the present disclosure includes, wherein themultiple of contra-rotating variable vanes are located between an outerring and an inner ring.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein the sync ring is located radially outboardof the outer ring.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes an actuator to rotate the sync ring.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein each of the multiple of contra-rotatingvariable vanes includes a control post and a pivot post that interactwith at least one of the outer ring and the inner ring.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein each of the multiple of contra-rotatingvariable vanes includes a control post and a pivot post that interactwith at least one of the outer ring and the inner ring, the control postinteracts with a non-linear slot in at least one of the outer ring andthe inner ring.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein each of the control posts from each of themultiple of contra-rotating variable vanes extends through a linear slotin the sync ring.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein each of the linear slots are locatedparallel to a central longitudinal engine axis.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein the non-linear slot alternatively extendsproximate either a leading edge or a trailing edge of each of themultiple of contra-rotating variable vanes.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein each of the control posts from each of themultiple of contra-rotating variable vanes extends through a linear slotin the sync ring.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein each of the linear slots are locatedparallel to a central longitudinal engine axis.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein the non-linear slot is alternativelylocated either forward or aft of a pivot aperture in the outer ring andthe inner ring.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein each of said control posts from each ofsaid multiple of contra-rotating variable vanes extends through a linearslot in said sync ring.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein each of said linear slots are locatedparallel to a central longitudinal engine axis.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein each of said control posts from each ofsaid multiple of contra-rotating variable vanes alternatively extendsproximate either a leading edge or a trailing edge of each of saidmultiple of contra-rotating variable vanes.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein each of said control posts from each ofsaid multiple of contra-rotating variable vanes extends through a linearslot in said sync ring.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein said airflow path is radially outboard of aprimary airflow path that exhausts through a convergent divergentnozzle.

A method of operating a gas turbine engine according to anotherdisclosed non-limiting embodiment of the present disclosure includesthrottling an annular airflow path with a multiple of contra-rotatingvariable vanes.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes rotating a sync ring to rotate each of the multipleof contra-rotating variable vanes through interaction with a respectivenon-linear slot in at least one of an inner ring or an outer ringdefined around the multiple of contra-rotating variable vanes.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes moving each of the multiple of contra-rotatingvariable vanes through interaction with a respective linear slot in thesync ring for each of the multiple of contra-rotating variable vanes.

The foregoing features and elements may be combined in variouscombinations without exclusivity, unless expressly indicated otherwise.These features and elements as well as the operation thereof will becomemore apparent in light of the following description and the accompanyingdrawings. It should be understood, however, the following descriptionand drawings are intended to be exemplary in nature and non-limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features will become apparent to those skilled in the art fromthe following detailed description of the disclosed non-limitingembodiment. The drawings that accompany the detailed description can bebriefly described as follows:

FIG. 1 is a general schematic view of an exemplary variable cycle gasturbine engine according to one non-limiting embodiment;

FIG. 2 is a perspective view of an annular airflow control systemaccording to one non-limiting embodiment;

FIG. 3 is a front view of the annular airflow control system in an openposition;

FIG. 4 is a front view of the annular airflow control system in a closedposition;

FIG. 5 is a front view of the annular airflow control system in anintermediate position;

FIG. 6 is a top schematic perspective view of the annular airflowcontrol system in an intermediate position without the outer ring andsync ring shown;

FIG. 7 is a top schematic perspective view of the annular airflowcontrol system in an intermediate position without the sync ring shown;

FIG. 8 is a top schematic perspective view of an inner ring of theannular airflow control system;

FIG. 9 is a top schematic perspective view of the annular airflowcontrol system in an intermediate position;

FIG. 10 is a top schematic phantom view of the annular airflow controlsystem in an open position;

FIG. 11 is a top schematic phantom view of the annular airflow controlsystem in a closed position; and

FIG. 12 is a top schematic phantom view of the annular airflow controlsystem in an intermediate position.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a gas turbine engine 20. The gasturbine engine 20 is disclosed herein as a variable cycle two-spoolbypass turbofan that generally includes: a fan section 22 with a firststage fan section 24 and a second stage fan section 26; a high pressurecompressor section 28; a combustor section 30; a high pressure turbinesection 32; a low pressure turbine section 34; an augmentor section 36;an annular airflow control system 38; an exhaust duct section 40; and anozzle section 42. Additional sections, systems and features such as ageared architecture that may be located in various engine sections, forexample, aft of the second stage fan section 26 or forward of the lowpressure turbine section 34. The sections are defined along a centrallongitudinal engine axis A. Variable cycle gas turbine engines poweraircraft over a range of operating conditions and essentially alters abypass ratio during flight to achieve countervailing objectives such ashigh specific thrust for high-energy maneuvers yet optimizes fuelefficiency for cruise and loiter operational modes.

The engine 20 generally includes a low spool 44 and a high spool 46 thatrotate about the engine central longitudinal axis A relative to anengine case structure 48. Other architectures, such as three-spoolarchitectures, will also benefit herefrom.

The engine case structure 48 generally includes an outer case structure50, an intermediate case structure 52 and an inner case structure 54. Itshould be understood that various structures individual or collectivelymay define the case structures 48 to essentially define an exoskeletonthat supports the spools 44, 46 for rotation therein.

The first stage fan section 24 communicates airflow into a third streamairflow path 56 as well as into a second stream airflow path 58 and acore primary airflow path 60 that is in communication with the augmentorsection 36. The second stage fan section 26 communicates at least inpart with the second stream airflow path 58 and the primary airflow path60. The fan section 22 may alternatively or additionally include otherarchitectures that, for example, include additional or fewer stages eachwith or without various combinations of variable or fixed guide vanes.

The core primary airflow is compressed by the first stage fan section24, the second stage fan section 26, the high pressure compressorsection 28, mixed and burned with fuel in the combustor section 30, thenexpanded over the high pressure turbine section 32 and the low pressureturbine section 34. The turbines sections 32, 34 rotationally drive therespective low spool 44 and high spool 46 in response to the expansion.Each of the turbine sections 32, 34 may alternatively or additionallyinclude other architectures that, for example, include additional orfewer stages each with or without various combinations of variable orfixed guide vanes.

The third stream airflow path 56 is generally annular in cross-sectionand defined by the outer case structure 50 and the intermediate casestructure 52. The second stream airflow path 58 is also generallyannular in cross-section and defined by the intermediate case structure52 and the inner case structure 54. The core primary airflow path 60 isgenerally circular in cross-section and defined by the inner casestructure 54. The second stream airflow path 58 is defined radiallyinward of the third stream airflow path 56 and the core primary airflowpath 60 is radially inward of the core primary airflow path 60. Variouscrossover and cross-communication airflow paths may alternatively oradditionally provided.

The exhaust duct section 40 may be circular in cross-section as typicalof an axis-symmetric augmented low bypass turbofan. Alternatively oradditionally, the exhaust duct section 40 may be non-axisymmetric incross-section or other shape and/or non-linear with respect to thecentral longitudinal engine axis A to form, for example, a serpentineshape to block direct view to the turbine section.

The nozzle section 42 may include a third stream exhaust nozzle 62(illustrated schematically) which receives flow from the third streamairflow path 56 and a mixed flow exhaust nozzle 64 (illustratedschematically) which receives a mixed flow from the second streamairflow path 58 and the core primary airflow path 60. It should beunderstood that various fixed, variable, convergent/divergent,two-dimensional and three-dimensional nozzle systems may be utilizedherewith.

With reference to FIG. 2, the annular airflow control system 38, in onedisclosed non-limiting embodiment is located within the third streamairflow path 56 in the region of the exhaust duct section 40 to controlthe third stream airflow. In the disclosed non-limiting embodiment, theannular airflow control system 38 throttles the airflow in the thirdstream airflow path 56. In one disclosed non-limiting embodiment, theannular airflow control system 38 may throttle the airflow down to aminimal but non-zero airflow to backpressure the third stream airflow.It should be appreciated that the annular airflow control system 38 maybe located in other airflow paths.

The annular airflow control system 38 includes a multiple ofcontra-rotating variable vanes 70 between an outer ring 72 and an innerring 74 with a sync ring 76 that is driven by an actuator 78(illustrated schematically) that operates in response to a control 80(illustrated schematically). It should be appreciated that various othercontrol components such as sensors, actuators and other subsystems maybe utilized herewith.

The actuator 78 may include a mechanical, electrical and/or pneumaticdrive that operates to rotate the sync ring 76 about the engine axis Aso as to move the annular airflow control system 38 between an openposition (FIG. 3) and a closed position (FIG. 4), through anintermediate position (FIG. 5). That is, the actuator 78 provides themotive force to rotate the sync ring 76 and thereby control an airflowstream in the third stream airflow path 56.

The control 80 generally includes a control module that executes anairflow control logic to thereby control the radial tip clearancerelative the rotating blade tips. The control module typically includesa processor, a memory, and an interface. The processor may be any typeof known microprocessor having desired performance characteristics. Thememory may be any computer readable medium which stores data and controlalgorithms such as logic as described herein. The interface facilitatescommunication with other components such as the actuator 78. In onenon-limiting embodiment, the control module may be a portion of a flightcontrol computer, a portion of a Full Authority Digital Engine Control(FADEC), a stand-alone unit or other system.

With reference to FIG. 6, each of the multiple of contra-rotatingvariable vanes 70 are defined by an outer airfoil wall surface 82between a leading edge 84 and a trailing edge 86 and an inner edge 88and an outer edge 90. In one disclosed non-limiting embodiment, theouter airfoil wall surface 82 may define a generally concave shapedportion to form a pressure side 92 and a generally convex shaped portionthat forms a suction side 94. It should be appreciated that variousairfoil and non-airfoil shapes may alternatively be provided.

Each of the multiple of contra-rotating variable vanes 70 includes anouter pivot post 96, an inner pivot post 98 and a control post 100. Theouter pivot post 96 and the inner pivot post 98 define a pivot axis Pabout which each of the multiple of contra-rotating variable vanes 70pivot. Each outer pivot post 96 and inner pivot post 98 extend through arespective aperture 102, 104 in the outer ring 72 (FIG. 7) and the innerring 74 (FIG. 8). That is, each of the multiple of contra-rotatingvariable vanes 70 pivot about a pivot axis P which defines the center ofrotation for each of the multiple of contra-rotating variable vanes 70.

The control post 100 may extend from the inner edge 88 and/or the outeredge 90 for respective interface with the outer ring 72 and/or the innerring 74 as well as the sync ring 76 (FIG. 9). The control post 100alternatively extends proximate either the leading edge 84 or a trailingedge 86 of each of the multiple of contra-rotating variable vanes 70.That is, of the one example contra-rotating variable vanes 70 that has acontrol post 100 which extends proximate the leading edge 84 will bebetween two contra-rotating variable vanes 70 that has the control post100 proximate the trailing edge 86. It should be appreciated thatalthough the control posts 100 are illustrated as extended from theouter edge 90, the control posts 100 may alternatively extend from theinner edge 88 with an associated inner sync ring 76 (not shown).

With reference to FIG. 7, each control post 100 of each of the multipleof contra-rotating variable vanes 70 extends through a respectivenon-linear slot 106 in the outer ring 72. Each non-linear slot 106 isgenerally arcuate with a center of the arc defined at the respectiveaperture 102 in the outer ring 72.

With reference to FIG. 9, each control post 100 of each of the multipleof contra-rotating variable vanes 70 further extends through arespective linear slot 108 in the sync ring 76. Each linear slot isoriented parallel to the central longitudinal engine axis A for an axiallength that generally corresponds with an axial length of the associatedrespective non-linear slot 106.

In operation, the actuator 78 rotates the sync ring 76. Each linear slot108 drives the respective control post 100 of each of the multiple ofcontra-rotating variable vanes 70 in its respective non-linear slot 106such that the multiple of contra-rotating variable vanes 70 are movedbetween the open position (FIG. 10) and the closed position (FIG. 11),through the intermediate position (FIG. 12) in a contra-rotating manner.

The annular airflow control system 38 readily controls airflow throughan annular airflow path to enhance engine operability and performance.Furthermore, the contra-rotating motion provides a relatively balancedresponse to the airflow to minimize actuator 78 power requirements.

The use of the terms “a” and “an” and “the” and similar references inthe context of description (especially in the context of the followingclaims) are to be construed to cover both the singular and the plural,unless otherwise indicated herein or specifically contradicted bycontext. The modifier “about” used in connection with a quantity isinclusive of the stated value and has the meaning dictated by thecontext (e.g., it includes the degree of error associated withmeasurement of the particular quantity). All ranges disclosed herein areinclusive of the endpoints, and the endpoints are independentlycombinable with each other. It should be appreciated that relativepositional terms such as “forward,” “aft,” “upper,” “lower,” “above,”“below,” and the like are with reference to the normal operationalattitude of the vehicle and should not be considered otherwise limiting.

Although the different non-limiting embodiments have specificillustrated components, the embodiments of this invention are notlimited to those particular combinations. It is possible to use some ofthe components or features from any of the non-limiting embodiments incombination with features or components from any of the othernon-limiting embodiments.

It should be appreciated that like reference numerals identifycorresponding or similar elements throughout the several drawings. Itshould also be appreciated that although a particular componentarrangement is disclosed in the illustrated embodiment, otherarrangements will benefit herefrom.

Although particular step sequences are shown, described, and claimed, itshould be understood that steps may be performed in any order, separatedor combined unless otherwise indicated and will still benefit from thepresent disclosure.

The foregoing description is exemplary rather than defined by thelimitations within. Various non-limiting embodiments are disclosedherein, however, one of ordinary skill in the art would recognize thatvarious modifications and variations in light of the above teachingswill fall within the scope of the appended claims. It is therefore to beunderstood that within the scope of the appended claims, the disclosuremay be practiced other than as specifically described. For that reasonthe appended claims should be studied to determine true scope andcontent.

What is claimed is:
 1. An annular airflow control system for a gasturbine engine comprising: a multiple of contra-rotating variable vanes;and a sync ring rotatable to move the multiple of contra-rotatingvariable vanes between an open position and a closed position tothrottle an airflow through said multiple of contra-rotating variablevanes.
 2. The system as recited in claim 1, wherein said multiple ofcontra-rotating variable vanes are located between an outer ring and aninner ring.
 3. The system as recited in claim 2, wherein said sync ringis located radially outboard of said outer ring.
 4. The system asrecited in claim 3, further comprising an actuator to rotate said syncring.
 5. The system as recited in claim 2, wherein each of said multipleof contra-rotating variable vanes includes a control post and a pivotpost that interact with at least one of said outer ring and said innerring.
 6. The system as recited in claim 2, wherein each of said multipleof contra-rotating variable vanes includes a control post and a pivotpost that interact with at least one of said outer ring and said innerring, said control post interacts with a non-linear slot in at least oneof said outer ring and said inner ring.
 7. The system as recited inclaim 6, wherein each of said control posts from each of said multipleof contra-rotating variable vanes extends through a linear slot in saidsync ring.
 8. The system as recited in claim 7, wherein each of saidlinear slots are located parallel to a central longitudinal engine axis.9. The system as recited in claim 6, wherein said non-linear slotalternatively extends proximate either a leading edge or a trailing edgeof each of said multiple of contra-rotating variable vanes.
 10. Thesystem as recited in claim 6, wherein each of said control posts fromeach of said multiple of contra-rotating variable vanes extends througha linear slot in said sync ring.
 11. The system as recited in claim 10,wherein each of said linear slots are located parallel to a centrallongitudinal engine axis.
 12. The system as recited in claim 6, whereinsaid non-linear slot is alternatively located either forward or aft of apivot aperture in said outer ring and said inner ring.
 13. The system asrecited in claim 12, wherein each of said control posts from each ofsaid multiple of contra-rotating variable vanes extends through a linearslot in said sync ring.
 14. The system as recited in claim 13, whereineach of said linear slots are located parallel to a central longitudinalengine axis.
 15. The system as recited in claim 6, wherein each of saidcontrol posts from each of said multiple of contra-rotating variablevanes alternatively extends proximate either a leading edge or atrailing edge of each of said multiple of contra-rotating variablevanes.
 16. The system as recited in claim 13, wherein each of saidcontrol posts from each of said multiple of contra-rotating variablevanes extends through a linear slot in said sync ring.
 17. The system asrecited in claim 1, wherein said airflow path is a third stream airflowpath.
 18. A method of operating a gas turbine engine comprising:throttling an annular airflow path with a multiple of contra-rotatingvariable vanes.
 19. The method as recited in claim 18, furthercomprising rotating a sync ring to rotate each of the multiple ofcontra-rotating variable vanes through interaction with a respectivenon-linear slot in at least one of an inner ring or an outer ringdefined around the multiple of contra-rotating variable vanes.
 20. Themethod as recited in claim 19, further comprising moving each of themultiple of contra-rotating variable vanes through interaction with arespective linear slot in the sync ring for each of said multiple ofcontra-rotating variable vanes.